1. Field of the Invention
The present invention relates in general to a thin film transistor liquid crystal display (THT-LCD). In particular, the present invention relates to a thin film transistor liquid crystal display generating voltage by capacitive coupling to form multiple domains.
2. Description of the Related Art
With liquid crystal display (LCD) applied to notebooks and monitors, the market for LCD is getting larger. When large, high resolution LCD panels are used for desktop monitors, wide viewing angle and quick response time is required.
For vertically aligned (VA) LCD, controlling the domain of the liquid crystal molecules to obtain a wider viewing angle for the LCD is an important technology. Most conventional LCDs are 90xc2x0 twisted nematic type (TN) LCD, which have LCD panel and polarizers pasted on the outer surface thereof. The disadvantage of the conventional LCD is that the visual angle is narrow (about xc2x140xc2x0 horizontal and xc2x130xc2x0 vertical), the response time is slow (about 50 ms), and the color dispersion is severe. Therefore, it is hard to obtain a good LCD panel by conventional technology. Moreover, rubbing during manufacture will cause electricity discharge and contamination.
To manufacture the LCD panel with wide viewing angle, the prior art has developed many kinds of VA LCD structures. For example, FIG. 1 shows the patterned VA (PVA) type LCD developed by Samsung Company. In FIG. 1, there are slits 14 on the upper electrode 10 and the lower electrode 12 to form the horizontal electric field around the slits 14. The curved lines in the FIG. 1 represent the electric potential lines perpendicular to the electric field. Therefore, the arrangement direction of the liquid crystal molecules, perpendicular to the substrate, is turned by the horizontal electric field to form different arrangement directions in different domains.
In addition, Fujitsu Company provides a LCD structure with multiple domains vertical alignment (MVA), which forms protrusions on the upper electrode to provide a pre-lean angle for the liquid crystal molecule to make the liquid crystal molecule form different arrangement directions in the different domains.
The prior art mentioned above can provide LCD with wide viewing angle, but requires additional processes to form the slits or protrusions on the color filter. Moreover, the higher accuracy of the alignment between the upper substrate and the lower substrate is required, and the manufacture process is more complicated.
In one aspect the present invention provides a thin film transistor liquid crystal display. A first substrate and a second substrate are provided, in which an enclosed space is formed between the first substrate and the second substrate. A liquid crystal layer is filled in the enclosed space. An upper electrode is formed on the inner surface of the first substrate. A lower electrode is formed on the inner surface of the second substrate having a first electrode and a pixel electrode beside the first electrode. The first electrode is coupled to a drain/source of a thin film transistor, and a portion of the pixel electrode is overlapped on the drain/source of the thin film transistor but insulated from the drain/source of the thin film transistor. A plurality of polarizers are formed on the outer surface of the first substrate and the second substrate respectively. In another aspect the present invention provides a TFT-LCD with multiple domains formed by the voltage difference between the lower electrodes, which generates voltage difference by capacitive coupling to control the domain. In addition, the voltage difference is generated between the lower electrodes without adding additional data lines. Therefore, the number of chips needed for driving is decreased and the design of the TFT array is simplified. Moreover, the structure of the upper electrodes does not require modification. Compared with the patterned VA type LCD provided by Samsung Company and the multiple domains vertical aligned type LCD provided by Fujitsu Company, the disclosed manufacture process is simplified.
Preferably, the lower electrode is separated into at least two electrodes, the narrow electrode and the pixel electrode. The pixel electrode can further be separated into more pixel electrodes. In addition, the narrow electrode is coupled to a drain/source of a thin film transistor, and a portion of the pixel electrode is overlapped on the drain/source of the thin film transistor but insulated to the thin film transistor. Therefore, capacitive coupling is preferably generated to make the voltage of the narrow electrode higher than the pixel electrode. Hence, the horizontal electric field is formed between the narrow electrode and the pixel electrode to generate a plurality of domains in a pixel. Additional processing is not required to form slits or protrusions on the color filter and a requirement for high accuracy of alignment between the upper substrate and the lower substrate can be overcome.